Steve, I'll look at my Winchester Single Shot books tomorrow morning and see if I can find out an answer to your question about how common/rare those actions were (Is it a flatspring or a coiled spring action? Aprox. SN?).
Just my opinion, but if I were you, I'd just keep it as a nice .22 with some history and a barrel by a great maker, unless it is in truly lousy shape.
You are going to have a heck of a time finding original Carbine parts, I suspect (a Winder musket stock will have an inletted sling swivel base and screw holes--very hard to rework to carbine style). I have built several 1885s from parts over the years and never have seen either a carbine barrel, stock, or forend for sale in about 50 years of looking. Even if you could find the parts, you would still have a "parts gun," with little collector value (or at least value not even close to an original carbine). And as a shooter, a .32 WCF carbine is an interesting little gun, but not good for much (Yours may well have done time in Oz as a "Stinger"!).
It is sad that this rare gun was "mutilated and mutated" but more fooling with it won't really bring it back. I have, as I said, put together several lowalls from parts (back when there WERE parts) and and none of them were more than fun hunting/informal target guns when I was done. (In my defense, Winchester collectors, I always started with SERIOUS train wrecks....my .25-20 WCF has parts from SEVEN rifles, plus some homemade and aftermarket parts).
